JP2011043797A - Particle dispersion liquid for display, display medium, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particle dispersion liquid for display superior in image retainability (memory ability). <P>SOLUTION: The particle dispersion liquid for display includes: a dispersion medium 50 containing silicone oil; particles of display (their particle group 34) which are dispersed in the dispersion medium, move in response to an electric field, and have a polar group on the surface; and non-charged silica particles (not shown) which are dispersed in the dispersion medium and have an alkyl group on the surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display particle dispersion, a display medium, and a display device.

  An electrophoretic display medium has been actively studied as a display having image maintenance (so-called memory property). In this display method, display particles (electrophoretic particles) charged in a liquid are used, and the electrophoretic particles are enclosed in a cell by applying an electric field (two electrode substrates are stacked and an electrophoretic material is enclosed with a dispersion medium therebetween). Display is performed by alternately moving to the viewing surface and back surface of the configuration.

  In the present technology, the display particles (electrophoretic particles) are important elements, and various technical developments have been made. For example, various techniques for imparting cohesive force to display particles and imparting image maintainability (so-called memory property) have been proposed (for example, Patent Documents 1 to 4).

Japanese Patent Application No. 2005-331859 Japanese Patent Application No. 2007-121570 Special table 2007-534006 gazette JP 2001-265261 A

  An object of the present invention is to provide a display particle dispersion having excellent image maintainability as compared with a case where an alkyl group is present on the surface and uncharged silica particles are not applied.

The above problem is solved by the following means. That is,
The invention according to claim 1
A dispersion medium containing silicone oil;
First display particles that are dispersed in the dispersion medium and move according to an electric field, the first display particles having a polar group on the surface,
Dispersed in the dispersion medium, having an alkyl group on the surface, and uncharged silica particles;
A particle dispersion for display comprising:

The invention according to claim 2
2. The display particle dispersion according to claim 1, comprising second display particles that are dispersed in the dispersion medium and move according to an electric field, and that have second display particles having a nonpolar group on the surface.

The invention according to claim 3
3. The display particle dispersion according to claim 1, wherein a polymer composed of a copolymer of a monomer having a polar group and a monomer having a silicone chain is dissolved in the dispersion medium.

The invention according to claim 4
A pair of substrates, at least one of which is translucent,
The display particle dispersion liquid according to any one of claims 1 to 3, encapsulated between the pair of substrates,
A display medium comprising:

The invention according to claim 5
A pair of electrodes, at least one of which is translucent,
The area | region which has the particle dispersion liquid for display of any one of Claims 1-3 provided between the said pair of electrodes,
A display medium comprising:

The invention according to claim 6
A display medium according to claim 4 or 5, and
Voltage application means for applying a voltage between the pair of substrates or the pair of electrodes of the display medium;
A display device comprising:

According to the first aspect of the present invention, it is possible to provide a display particle dispersion that has an alkyl group on the surface and is excellent in image maintainability as compared with the case where uncharged silica particles are not applied.
The invention according to claim 2 can provide a display particle dispersion excellent in image maintainability as compared with the case where the second display particles having no polar group on the surface are not applied as the second display particles.
The invention according to claim 3 is a display excellent in image maintainability compared with a case where a polymer composed of a copolymer of a monomer having a polar group and a monomer having a silicone chain is not dissolved in a dispersion medium. A particle dispersion can be provided.
According to the inventions according to claims 4, 5, and 6, the display medium having an alkyl group on the surface of the display particle dispersion and having excellent image maintainability compared to a case where uncharged silica particles are not applied, A display device can be provided.

It is a schematic block diagram of the display apparatus which concerns on this embodiment. It is explanatory drawing which shows typically the movement aspect of a particle group when a voltage is applied between the board | substrates of the display medium of the display apparatus which concerns on this embodiment. It is a figure which shows the relationship between the density | concentration of a silica particle, and the diameter (aggregation diameter) of the particle for a display. It is a schematic diagram for demonstrating bridging aggregation. It is a schematic diagram for demonstrating exhaustion aggregation. It is a schematic diagram for demonstrating bridging aggregation. It is a schematic diagram for demonstrating bridging aggregation when a mediating polymer is used.

  Hereinafter, embodiments of the present invention will be described.

(Particle dispersion for display)
The display particle dispersion according to this embodiment includes a dispersion medium containing silicone oil, and first display particles that are dispersed in the dispersion medium and move according to an electric field, and have a polar group on the surface. Particles for use, and silica particles that are dispersed in a dispersion medium, have an alkyl group on the surface, and are uncharged.

  In the display dispersion according to the present embodiment, in a system in which an alkyl group on the surface and uncharged silica particles are dispersed in a dispersion medium containing silicone oil, display particles having a polar group on the surface in the system. Is dispersed, it is considered that aggregation of the display particles is likely to occur even if the display particles are charged to the same polarity. This is because, in a dispersion medium containing silicone oil, together with display particles having a polar group on the surface, silica particles having an alkyl group on the surface and having no charge are dispersed in the dispersion medium. As shown, in a low concentration region of silica particles, an action called bridging aggregation (crosslinking aggregation) occurs on the first display particles having a polar group on the low surface, and depletion occurs when the concentration of silica particles increases. This is probably because an action called aggregation occurs.

  FIG. 3 is a diagram showing the relationship between the concentration of silica particles and the diameter (aggregation diameter) of display particles. As shown in FIG. 3, as the concentration of the silica particles increases, the size of the display particle diameter (aggregation diameter) has two peaks. It is considered that bridging aggregation (crosslinking aggregation) of the display particles due to the silica particles occurs at the peak of the diameter (aggregation diameter) of the display particles on the low concentration side of the silica particles. On the other hand, at the peak of the diameter (aggregation diameter) of the display particles on the high concentration side of the silica particles, it is considered that the display particles are depleted and aggregated by the silica particles.

  In addition, in the concentration range of the silica particles sandwiched between the two peaks of the display particle size (aggregation diameter), it is not clear whether the agglomeration effect on the display particles is working, but the silica particles are dispersed. Compared with the case where it is not added to the liquid, it becomes easier to agglomerate, so it is presumed that some aggregating action occurs.

Here, in bridging aggregation (crosslinking aggregation), the display particles approach each other from the state in which the display particles having polar groups are separated and dispersed in the dispersion medium (FIG. 4A). When there are uncharged silica particles having an alkyl group on the surface, the silica particles adhere to the surface of the display particles, and the display particles close to each other are bridged and aggregated. This is considered to be an action (see FIG. 4B). The surface of the silica particles is in a state in which an alkyl group is bonded to siloxane, which has a structure equivalent to that of silicone oil, so that the silica particles are very familiar with silicone oil and have high dispersibility. In addition, the alkyl group on the surface of the silica particle creates a stochastic gap by thermal motion, and there is a siloxane main chain and an unreacted silanol group at the back of the gap (for example, the inner wall surface of the silica particle surface). It is considered that the polar group of the display particles causes bridging aggregation due to van der Waals force or coordination bond (see FIG. 6).
An example of this state is schematically shown in FIG. In FIG. 6, for example, the polar group of a display particle having a polymer emulsifier having a polar group (indicated by —NR ₂ in FIG. 6) attached to the surface is the movement of the display particle or the segment motion of the polymer emulsifier. By approaching the silanol groups (its OH groups) present on the inner surface of the pores of the silica particles whose surfaces are alkylated, the polar groups on the surface of the display particles and the silanol groups (the OH groups) of the silica particles Group) exerts an attractive action by van der Waals force or coordination bond, and schematically shows that bridging aggregation occurs.
However, it is considered that the bonding force as a whole particle is relatively weak because it is easily cut due to bonding with a small gap and there are few binding sites. If siloxane or silanol groups are exposed on the surface of the silica particles, the bonds between the silica particles and the display particles having polar groups become strong, resulting in irreversible aggregation, and reversible aggregation as shown in FIG. 3 does not occur. It is not considered. Further, it is considered that silica particles cannot exist in a dispersed state in silicone oil when the polar group is exposed. That is, it can be said that the uncharged silica particles having an alkyl group on the surface are in a state in which the balance between the dispersion and the cohesive force is balanced.

  When the concentration of the silica particles increases, in the dispersion liquid containing silicone oil, the polar groups of the display particles and the alkyl groups of the silica particles are caused by, for example, van der Waals force or coordination bond, so that the silica particles become display particles. It is considered that the silica particles that adhere to the surface and cannot be attached when the concentration exceeds the saturated adsorption concentration are dispersed in the dispersion medium (FIG. 5A). In this state, when the display particles are close to each other at a distance smaller than the diameter of the silica particles in a state where the display particles to which the silica particles are adhered and are not completely adhered are dispersed, the silica particles are removed from between the display particles. It becomes easy to be excluded (in other words, it becomes difficult for the silica particles to enter between the display particles), and there is a region where the silica particles are depleted. At this time, since there are more dispersion media between the display particles that are close to each other than between the display particles that are close to each other, the display particles are pushed from around and easily cause aggregation (see FIG. 5 (B)). This is called a depletion effect, and the resulting aggregation is said to be depletion aggregation (see, for example, Patent Document 1 above).

Therefore, in the display particle dispersion according to the present embodiment, and the display medium and the display device using the display particle dispersion, the image maintenance is performed as compared with the case where the silica particles are not applied due to the aggregation action of the display particles by the silica particles. It is thought that it will be excellent in performance (memory properties).
In addition, the aggregating action of the display particles by the silica particles can be easily canceled by the movement of the display particles according to the electric field, and it is considered that the display by the movement of the display particles can be realized repeatedly.
In addition, the aggregating action of the display particles by the silica particles does not depend on the amount of charge in principle, so the degree of freedom of configuration of the display medium and the display device is increased. It is considered that the image density can be improved because of the action.

  Here, the polymer (dispersant etc.) can cause the bridging aggregation (crosslinking aggregation) and the depletion aggregation to the display particles. The aggregation action by the polymer is caused by the addition of the polymer. The dispersion medium tends to increase in viscosity, change in cohesive force with temperature, and irreversible aggregation. On the other hand, the agglomeration effect by the silica particles hardly increases the viscosity of the dispersion medium due to the addition of the silica particles, hardly changes in the agglomeration force due to temperature, is likely to be reversible agglomeration (aggregation is easily released), This is advantageous compared to the aggregating action by molecules.

  On the other hand, the display particle dispersion according to the present embodiment may include two or more display particles as display particles. Examples of the two or more kinds of display particles include display particles having different charging polarities and combinations of display particles having different electric field strengths that start moving by an electric field. In particular, in the display particle dispersion according to this embodiment, the second display particles dispersed in the dispersion medium together with the first display particles and moving according to the electric field have a nonpolar group on the surface. A form in which display particles are used in combination is preferable.

  The second display particles are display particles having a nonpolar group on the surface. For this reason, it is considered that the siloxane main chain and the unreacted silanol group existing in the back of the gap between the nonpolar group of the second display particles and the alkyl group of the silica particles hardly interact. By using the second display particles together with the first display particles, the image retention of the first display particles, the image retention of the second display particles, and other characteristics can be easily controlled independently. On the other hand, when the second display particles have a polar group, bridging aggregation or the like is caused together with the first display particles, and it is considered difficult to independently drive each of them. Therefore, it is considered that the image maintaining property (memory property) is excellent as compared with the case where the second display particles having no polar group on the surface are not applied as the second display particles. It is also considered that the color developability is excellent.

  Here, the reason for the second display particles is not clear, but when the silica particles adhere to the first display particles, the first display particles behave as negatively charged particles. Positively charged particles).

  In addition, the display particle dispersion according to this embodiment includes a polymer (hereinafter referred to as a mediator) made of a copolymer of a monomer having a polar group and a monomer having a silicone chain in a dispersion medium (silicone oil). The polymer may be dissolved. By dissolving the mediator polymer in the dispersion medium, the mediator polymer causes bridging agglomeration (crosslinking agglomeration) between the first display particles and the silica particles, strengthening the agglomeration force of these particles, and maintaining the image. It is considered that the property (memory property) will be excellent.

Here, as described above, bridging agglomeration (crosslinking agglomeration) due to silica particles is caused by van der Waals forces, coordination bonds, etc., where polar groups on the surface of display particles and unreacted silanol groups on the surface of silica particles However, if a mediating polymer is interposed between the display particles and the silica particles, the polar groups on the surface of the display particles and the unreacted silanol groups on the surface of the silica particles, Each polar group is considered to have attractive effects such as van der Waals force and coordination bond.
An example of this state is schematically shown in FIG. In FIG. 7, for example, a mediating polymer having a polar group (indicated as —OH and —NR ₂ in FIG. 7) is interposed between the display particles and the silica particles, and the polar group of the mediating polymer is displayed. silanol groups but the polar group and the surface of the polar groups (title to FIG 7 -NR ₂₎ display particles adhered with polymer emulsifier surface having exists in an inner wall of a hole at the surface of the alkylated silica particles It schematically shows that bridging agglomeration occurs due to an attractive action by each of (the OH group) and van der Waals force or coordination bond. In FIG. 7, R represents an alkyl group.
The attractive action due to the polar group of the intermediary polymer is a phenomenon under a low dielectric solvent such as silicone oil (for example, dielectric constant of 5.0 or less), so only the combination of —OH · —NR ₂ shown in FIG. For example, it is considered that a combination of —OH · —OH, —NR ₂ · —NR ₂ , —COOH · —COOH, and —NR ₂ · —COOH results in the intermediate polymer having a polar group. It is considered that the bridging aggregation is caused.
For this reason, even if the display particles and the silica particles are separated from each other by a certain distance, bridging aggregation occurs, and the aggregation force increases and the image maintainability (memory property) becomes excellent. Conceivable.

  Hereinafter, each component will be described in detail.

First, silica particles will be described.
Silica particles are uncharged silica particles having an alkyl group on the surface. Specific examples of the silica particles include particles obtained by subjecting the surface of silica particles not subjected to surface treatment (hereinafter referred to as untreated silica particles) to alkylation with an alkylating agent. Note that “uncharged” does not have any charge polarity. Specifically, for example, the surface of the silica particles does not have a charging group such as a charging group, and the particles are It means that no movement occurs in response to an electric field.

Examples of the untreated silica particles include silica particles (silica single particles, silica composite oxide particles (for example, mixed crystal particles of SiO ₂ and TiO ₂ , Al ₂ O ₃ , TiO ₂ , Al ₂ O _3, etc.). particles coated with SiO _2, etc.) in the particle. silica particles, fumed silica particles, it may be any of wet silica particles.

  The untreated silica particles are preferably monodispersed and spherical silica particles (hereinafter referred to as monodispersed spherical silica). Here, monodispersion is discussed in terms of the standard deviation with respect to the average particle diameter including aggregates, and the standard deviation means that the volume average particle diameter is D50 × 0.22 or less. Further, the term “spherical” refers to Wadell's degree of sphericity, which means that the degree of sphericity is 0.6 or more, and is preferably 0.8 or more. Monodispersed spherical silica particles are obtained by a sol-gel method that is a wet method. The true specific gravity of the silica particles obtained by the sol-gel method is controlled to be lower than that of the vapor phase oxidation method because it is prepared by a wet method and without firing. In addition, the true specific gravity of the silica particles can be adjusted by controlling the type of hydrophobic treatment agent or the amount of treatment in the hydrophobization treatment step. The particle size of the silica particles is controlled by the hydrolysis of the sol-gel method, the weight ratio of alkoxysilane, ammonia, alcohol, water in the condensation polymerization step, the reaction temperature, the stirring rate, and the supply rate. Monodisperse and spherical shapes are also achieved by making this technique.

On the other hand, as an alkylating agent, tetraalkoxysilane or a partial hydrolysis condensate thereof, or a combination thereof; a cohydrolysis or condensation reaction product of a compound having a hydrolyzable silyl group and a hydrophilic group, silazane compound, silane Examples thereof include a compound or a combination thereof.
Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetrabutoxysilane. Examples of the partially hydrolyzed condensate of tetraalkoxysilane include alkyl silicates such as methyl silicate and ethyl silicate. These tetraalkoxysilanes may be used alone or in combination of two or more.
As a silazane compound, what is an alkyl group, a phenyl group, etc. as a group couple | bonded with a silicon atom is mentioned.
Here, the alkyl group introduced into the surface of the untreated silica particles alkylated using the alkylating agent (that is, the alkyl group that the silica particles have on the surface) has, for example, 1 to 20 carbon atoms. The carbon number is preferably 1 or more and 12 or less, and particularly preferably 1 or more and 8 or less.

  An example of a method for producing silica particles having an alkyl group on the surface is as follows. For example, first, a silane compound (for example, tetramethoxysilane) is dropped and stirred while applying temperature using ammonia water as a catalyst in the presence of water and alcohol. Do. Next, the silica sol suspension obtained by the reaction is centrifuged to separate into wet silica gel, alcohol and aqueous ammonia. A solvent is added to wet silica gel to form a silica sol again, an alkylating agent is added, and the silica surface is alkylated. Next, the target silica particles (for example, monodispersed spherical silica particles) are obtained by removing the solvent from the alkylated silica sol, drying, and sieving. Moreover, you may process again to the silica particle obtained in this way.

Here, examples of the silane compound include water-soluble compounds. Examples of the silane compound include compounds represented by the following chemical structural formula.
Formula: R _a SiX _4-a
(In the formula, a is an integer of 0 to 3, R represents an organic group such as a hydrogen atom, an alkyl group and an alkenyl group, and X represents a hydrolyzable group such as a chlorine atom, a methoxy group and an ethoxy group. To express.)

  As the silane compound, any type of chlorosilane, alkoxysilane, silazane, and special silylating agent may be used. Specifically, for example, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxy Silane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N -Bis (trimethylsilyl) urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinylto Ethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ- Typical examples include mercaptopropyltrimethoxysilane and γ-chloropropyltrimethoxysilane.

The particle size of the silica particles is smaller than the particle size of the display particles, for example, preferably 1/1000 or more and 1/2 or less, more preferably 1/500 or more and 1 / less than the particle size of the display particles. It is good that it is 3 or less. Specifically, the particle diameter of the silica particles is, for example, preferably from 5 nm to 5 μm in volume average particle diameter, and more preferably from 10 nm to 2 μm.
This volume average particle diameter was obtained by accumulating the volume average particle diameter of each obtained channel from the smaller one using the FPAR-1000: particle diameter analyzer manufactured by Otsuka Electronics Co., Ltd. The particle size. The same applies hereinafter.

  The concentration of the silica particles is preferably not less than the concentration at which bridging aggregation occurs (the lower limit concentration) (for example, 0.001% by mass or more based on the dispersion medium). In particular, the concentration of silica particles is a concentration at which bridging aggregation occurs (for example, 0.01% by mass or more and 10% by mass or less, preferably 0.05% by mass or more and 5% by mass or less with respect to the dispersion medium) or the above depletion. The concentration may cause aggregation (for example, 0.01% by mass or more and 50% by mass or less, and preferably 0.1% by mass or more and 30% by mass or less) with respect to the dispersion medium.

Next, display particles (first display particles, second display particles) will be described.
First, the first display particles will be described.
The first display particles are particles having a polar group on the surface, and include, for example, a colorant and a polymer having a polar group, and, if necessary, include other compounding materials. Is done. The display particles may be particles in which a colorant is dispersed and blended in a polymer, or may be particles in which a polymer is coated or adhered to the particle surface of the colorant.

  The polymer having a polar group preferably has a base or an acid group as the polar group (polarizable functional group). Here, in the polymer, the polar group may be a group that functions as a charging group, or may be a group that functions separately from a group that functions as a charging group, but is a group that functions as a charging group. Is good. When the polymer has a base or an acid group separately from a group that functions as a charging group, the charging group includes a fluorine group.

  Examples of the base (hereinafter, cationic group) as the polar group include an amino group and a quaternary ammonium group (including salts of these groups). Examples of the acid group (hereinafter, anionic group) as the polar group include a phenol group, a carboxyl group, a carboxylate group, a sulfonate group, a sulfonate group, a phosphate group, a phosphate group, and a tetraphenylboron group. (Including salts of these groups). In addition, when a cationic group functions as a charged group, for example, a positively charged polarity is easily imparted to the particles. On the other hand, when the anionic group functions as a charged group, for example, a negatively charged polarity is easily imparted to the particles.

  Specifically, the polymer having a polar group (charged group) may be, for example, a homopolymer of a monomer having a polar group (charged group) or a single polymer having a polar group (charged group). And a copolymer of a monomer and another monomer (a monomer having no polar group). The description such as “(meth) acrylate” is an expression including both “acrylate” and “methacrylate”. The same applies hereinafter.

  Examples of the monomer having a polar group (charged group) include a monomer having a cationic group (hereinafter referred to as a cationic monomer) and a monomer having an anionic group (hereinafter referred to as an anionic monomer). Can be mentioned.

Examples of the cationic monomer include the following. Specifically, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N, N-hydroxyethylaminoethyl (meta) ) Acrylate, N-ethylaminoethyl (meth) acrylate, N-octyl-N-ethylaminoethyl (meth) acrylate, N, N-dihexylaminoethyl (meth) acrylate and other aliphatic amino groups (meth) Acrylates, aromatic substituted ethylene monomers having nitrogen-containing groups such as dimethylaminostyrene, diethylaminostyrene, dimethylaminomethylstyrene, dioctylaminostyrene,
Vinyl-N-ethyl-N-phenylaminoethyl ether, vinyl-N-butyl-N-phenylaminoethyl ether, triethanolamine divinyl ether, vinyl diphenylaminoethyl ether, N-vinylhydroxyethylbenzamide, m-aminophenyl vinyl ether Nitrogen-containing vinyl ether monomers such as vinylamine, pyrroles such as N-vinylpyrrole, pyrrolines such as N-vinyl-2-pyrroline and N-vinyl-3-pyrroline, N-vinylpyrrolidine, vinylpyrrolidine aminoether Pyrrolidines such as N-vinyl-2-pyrrolidone, imidazoles such as N-vinyl-2-methylimidazole, imidazolines such as N-vinylimidazoline, indoles such as N-vinylindole, N-vinylindoline, etc. India Phosphorus, N-vinylcarbazole, carbazoles such as 3,6-dibromo-N-vinylcarbazole, pyridines such as 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, (meth) acrylic Piperidines such as piperidine, N-vinylpiperidone and N-vinylpiperazine, quinolines such as 2-vinylquinoline and 4-vinylquinoline, pyrazoles such as N-vinylpyrazole and N-vinylpyrazoline, and oxazoles such as 2-vinyloxazole , Oxazines such as 4-vinyloxazine and morpholinoethyl (meth) acrylate.
Moreover, as a particularly preferable cationic monomer from versatility, (meth) acrylates having an aliphatic amino group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate In particular, it is preferable to use a quaternary ammonium salt structure before or after polymerization. Quaternary ammonium chloride can be obtained, for example, by reacting the compound with alkyl halides or tosylate esters.

As an anionic monomer, the following are mentioned, for example.
Specifically, among the anionic monomers, carboxylic acid monomers include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, or anhydrides thereof and monoalkyl esters thereof. And vinyl ethers having a carboxyl group such as carboxyethyl vinyl ether and carboxypropyl vinyl ether.
Examples of the sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) click acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and salts thereof. There is. In addition, there are sulfuric acid monoesters of 2-hydroxyethyl (meth) acrylic acid and salts thereof.
Examples of phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl phosphate, diphenyl There are 2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, and the like.
Desirably, the anionic monomer has (meth) acrylic acid or sulfonic acid, and more desirably has an ammonium salt structure before or after polymerization. The ammonium salt is prepared by, for example, reacting with a tertiary amine or quaternary ammonium hydroxide.

  Here, as a monomer having a fluorine group that functions as a charging group other than a polar group (acid group and base), for example, there is a (meth) acrylate monomer having a fluorine group, specifically, trifluoroethyl ( (Meth) acrylate, pentafluoropropyl (meth) acrylate, perfluoroethyl (meth) acrylate, perfluorobutylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, perfluorodecylethyl (meth) acrylate, trifluoromethyl Examples thereof include trifluoroethyl (meth) acrylate and hexafluorobutyl (meth) acrylate.

  On the other hand, examples of other monomers include nonionic monomers (nonionic monomers). For example, (meth) acrylonitrile, (meth) acrylic acid alkyl ester, (meth) acrylamide, ethylene, propylene , Butadiene, isoprene, isobutylene, N-dialkyl substituted (meth) acrylamide, styrene, vinyl carbazole, styrene, styrene derivatives, polyethylene glycol mono (meth) acrylate, vinyl chloride, vinylidene chloride, isoprene, butadiene, vinyl pyrrolidone, hydroxyethyl ( Examples include meth) acrylate and hydroxybutyl (meth) acrylate.

  Here, the copolymerization ratio between the monomer having a polar group (charging group) and another monomer is changed according to the charge amount of the desired particles. Usually, the copolymerization ratio of the monomer having a polar group (charged group) and another monomer is selected in the range from 1: 100 to 100: 0 in terms of the molar ratio.

  The weight average molecular weight of the polymer having a polar group (charged group) is preferably from 1,000 to 1,000,000, more preferably from 10,000 to 200,000.

  Next, the colorant will be described. Examples of the colorant include organic or inorganic pigments, oil-soluble dyes, etc., for example, magnetic powders such as magnetite and ferrite, carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan colorants, azo Known colorants such as a yellow color material, an azo magenta color material, a quinacridone magenta color material, a red color material, a green color material, and a blue color material can be used. Specifically, examples of the colorant include aniline blue, calcoyl blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3, etc. are exemplified as typical examples.

  The blending amount of the colorant is preferably 10% by mass or more and 99% by mass or less, and more preferably 30% by mass or more and 99% by mass or less with respect to the polymer having a polar group (charging group).

Next, other compounding materials will be described. Examples of other compounding materials include a charge control material and a magnetic material.
As the charge control material, known materials used for electrophotographic toner materials can be used. For example, cetylpyridyl chloride, BONTRON P-51, BONTRON P-53, BONTRON E-84, BONTRON E-81 (above, Quaternary ammonium salts such as Orient Chemical Industry Co., Ltd., salicylic acid metal complexes, phenol condensates, tetraphenyl compounds, metal oxide particles, and metal oxide particles surface-treated with various coupling agents.

As the magnetic material, a color-coated inorganic magnetic material or organic magnetic material is used as necessary. Further, a transparent magnetic material, in particular, a transparent organic magnetic material is more preferable because it hardly inhibits the coloring of the colored pigment and has a smaller specific gravity than the inorganic magnetic material.
Examples of the colored magnetic material (color-coated material) include small-diameter colored magnetic powder described in JP-A-2003-131420. A material provided with magnetic particles serving as nuclei and a colored layer laminated on the surface of the magnetic particles is used. The colored layer may be selected such that the magnetic powder is opaquely colored with a pigment or the like, but it is preferable to use, for example, a light interference thin film. This optical interference thin film is a thin film having a thickness equivalent to the wavelength of light made of an achromatic material such as SiO ₂ or TiO ₂ and selectively reflects the wavelength of light by optical interference in the thin film. It is.

  Here, the first display particles may be particles in which a polymer emulsifier is attached (for example, bonded or coated) to the surface thereof. Alternatively, the polymer emulsifier may have a polar group (charged group) similar to the polymer constituting each of the display particles, and may be used in place of each of the above polymers constituting the display particle.

  Typical examples of the polymer emulsifier include silicone polymers. The silicone polymer is, for example, a polymer compound having a silicone chain, and more specifically, a compound having a silicone chain (silicone graft chain) as a side chain with respect to the main chain of the main polymer compound. Is good.

  Examples of silicone polymers include, for example, a silicone chain component, a reactive component as necessary, a copolymer component having a polar group (charged group), and other copolymer components (a copolymer having no polar group). A copolymer obtained by copolymerizing at least one component) is preferably used. In addition, a monomer may be used for the raw material of the copolymerization component (especially silicone chain component) in the said copolymer, and a macromonomer may be used. This "macromonomer" is a generic term for oligomers having a polymerizable functional group (degree of polymerization of about 2 or more and about 300 or less) or polymers, and has the properties of both polymers and monomers. is there.

  As the silicone chain component, a dimethyl silicone monomer having a (meth) acrylate group at one end (for example, manufactured by Chisso: Silaplane: FM-0711, FM-0721, FM-0725, etc., Shin-Etsu Silicone Co., Ltd .: X -22-174DX, X-22-2426, X-22-2475, etc.).

  Examples of the reactive component include glycidyl (meth) acrylate having an epoxy group, and isocyanate monomers having an isocyanate group (Showa Denko: Karenz AOI, Karenz MOI).

  As a copolymer component having a polar group (charged group) and other copolymer components (a copolymer component having no polar group), the polar group (charged group) described in the polymer having the polar group (charged group). And those mentioned for other monomers (monomers having no polar group) are applied.

  In the silicone polymer, the mass ratio of the silicone chain component to the whole polymer is 3% or more and 60% or less, preferably 5% or more and 40% or less.

  Examples of the silicone polymer include a silicone compound having an epoxy group at one end (silicone compound represented by the following structural formula 1) in addition to the copolymer. Examples of the silicone compound having an epoxy group at one end include X-22-173DX manufactured by Shin-Etsu Silicone Co., Ltd.

In Structural Formula 1, R ₁ ′ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. n represents a natural number (for example, 1 to 1000, preferably 3 to 100). x represents an integer of 1 to 3.

  Examples of the silicone polymer include a dimethyl silicone monomer having a (meth) acrylate group at one end (silicone compound represented by the following structural formula 2: manufactured by Chisso Corporation: Silaplane: FM-0711, FM-0721, FM -7725, Shin-Etsu Silicone Co., Ltd .: X-22-174DX, X-22-2426, X-22-2475, etc.) and glycidyl (meth) acrylate or isocyanate monomer (Showa Denko: Karenz AOI, Karenz MOI) A copolymer comprising at least two components is also preferred.

In Structural Formula 2, R ₁ represents a hydrogen atom or a methyl group. R ₁ ′ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. n represents a natural number (for example, 1 to 1000, preferably 3 to 100). x represents an integer of 1 to 3.

  The weight average molecular weight of the silicone polymer is desirably 500 or more and 1,000,000 or less, and more desirably 1,000 or more and 1,000,000 or less.

Among the first display particles described above, as the most preferable particles,
1) Particles in a form in which a polymer emulsifier having a polar group is attached to the surface of particles composed of a colorant and a polymer having a charged group,
2) Particles in a form in which a polymer emulsifier having a polar group and a charged group is attached to the surface of a particle composed of a colorant and a polymer having a nonpolar group,
3) Particles in a form in which a polymer emulsifier having a polar group is attached to the surface of a particle composed of a colorant having a charged group and a polymer having a nonpolar group,
4) Particles with a colorant embedded in a polymer having a charged group and a polar group,
5) Particles in a form in which a colorant having a charged group is embedded in a polymer having a polar group,
Etc.

Next, the second display particles will be described.
The second display particle is a particle having a nonpolar group (for example, a phenyl group, an alkyl group, or a derivative thereof) on the surface, and includes, for example, a colorant and a polymer having a nonpolar group. If necessary, it is configured to include other compounding materials. The display particles may be particles in which a colorant is dispersed and blended in a polymer, or may be particles in which a polymer is coated or adhered to the particle surface of the colorant.

The second display particles have the same basic material configuration as the first display particles except that they have nonpolar groups instead of polar groups.
Examples of the polymer (nonpolar polymer) constituting the second display particles include (alkyl) acrylic acid alkyl ester, ethylene, propylene, butadiene, isoprene, isobutylene, styrene, vinyl carbazole, styrene, and derivatives thereof. Can be mentioned.

The entire second display particle may be composed of a nonpolar polymer, or the core polymer may be composed of a polymer having a polar group, and an emulsifier made of a nonpolar polymer may be adhered (adsorbed). .
That is, as the most suitable form of particles as the second display particles,
1) Particles in a form in which a polymer emulsifier having a nonpolar group is attached to the surface of particles composed of a colorant and a polymer having a charged group,
2) Particles in a form in which a polymer emulsifier having a nonpolar group and a charged group is attached to the surface of a particle composed of a colorant and a polymer having a nonpolar group,
3) Particles in a form in which a polymer emulsifier having a nonpolar group is attached to the surface of a particle composed of a colorant having a charged group and a polymer having a nonpolar group,
4) Particles in a form in which a colorant having a charged group is embedded in a polymer having a nonpolar group,
Etc.

Next, the dispersion medium will be described.
The dispersion medium is configured to include silicone oil. Of course, the dispersion medium may be a mixed solvent of silicone oil and a solvent other than silicone oil.

  Specific examples of the silicone oil include silicone oils in which a hydrocarbon group is bonded to a siloxane bond (for example, dimethyl silicone oil, diethyl silicone oil, methyl ethyl silicone oil, methyl phenyl silicone oil, diphenyl silicone oil, etc.). Of these, dimethyl silicone is particularly desirable.

  Examples of the solvent other than silicone oil include other petroleum-derived high-boiling solvents such as paraffinic hydrocarbon solvents and fluorine-based liquids.

Next, the mediator polymer will be described.
The intermediate polymer is a copolymer of a monomer having a polar group and a monomer having a silicone chain.

  Examples of the monomer having a polar group include a monomer having an anionic group, a monomer having a cationic group, and other nonionic groups (for example, a hydroxyl group (-OH group)) described in the display particles. And the like [for example, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate).

  Examples of the monomer having a silicone chain include the monomers listed for the silicone chain component described above for the polymer emulsifier.

Specifically, as the mediator polymer, for example,
1) a copolymer of a monomer having a polar group and a monomer having a silicone chain;
2) a copolymer of two or more monomers having different polar groups and a monomer having a silicone chain;
Are preferable.

1) As a copolymer of one type of monomer having a polar group and a monomer having a silicone chain, for example, an amino group, a carboxyl group, an ester group, a hydroxyl group, a sulfonic acid group, Alternatively, a copolymer of a monomer having a sulfonate group or the like and a monomer having a silicone chain is preferably exemplified.
In the case of this copolymer, for example, the monomer ratio (mass ratio) is such that one kind of monomer having a polar group with respect to the monomer having a silicone chain is 0.1% by mass or more and 70% by mass. The following is preferable, and is preferably 0.2% by mass or more and 50% by mass or less.
In the case of this copolymer, the content of the intermediate polymer is preferably 0.01% by mass or more and 30% by mass or less, more preferably 0.05% by mass or less, more preferably 20% by mass or less with respect to the dispersion medium. It is 0.1 mass% or more and 10 mass% or less.

2) As a copolymer of two or more monomers having different polar groups and a monomer having a silicone chain, for example, 1) a monomer having an amino group and, for example, hydroxyl Copolymer of a monomer having a group, a carboxyl group, an ester group, a sulfonic acid group or a sulfonate group and a monomer having a silicone chain, 2) a carboxyl group, an ester group, a hydroxyl group, a sulfonic acid Among monomers having a group or a sulfonate group, a copolymer of any two or more monomers and a monomer having a silicone chain may be mentioned.
In the case of this polymer, for example, the monomer ratio (mass ratio) is such that the total of two or more monomers having a polar group with respect to the monomer having a silicone chain is 0.1% by mass. The content is preferably 70% by mass or less, and more preferably 0.2% by mass or more and 50% by mass or less.
The monomer ratio (mass ratio) of two or more types of monomers having polar groups is 0 for each monomer having one polar group and other monomers having a polar group. It is preferably 1% by mass or more and 99% by mass or less, and more preferably 5% by mass or more and 95% by mass or less.
In the case of this copolymer, the content of the intermediate polymer is preferably 0.01% by mass or more and 30% by mass or less, more preferably 0.05% by mass or less, more preferably 20% by mass or less with respect to the dispersion medium. It is 0.1 mass% or more and 10 mass% or less.

Next, a method for producing display particles (first and second display particles) will be described.
Examples of the method for producing display particles according to the present embodiment include a polymer, a colorant, a first solvent (a poor solvent capable of forming a continuous phase), and the first solvent incompatible with the first solvent. A step of stirring and emulsifying a mixed solution containing a second solvent having a boiling point lower than that of the solvent and dissolving the polymer (a good solvent capable of forming a dispersed phase), and the second solvent from the emulsified mixed solution. And a step of producing colored particles (display particles) containing the polymer and the colorant by removal. This manufacturing method is a so-called submerged drying method.

  In this production method, a dispersion medium (silicone oil) used for a display medium as a first solvent may be used as it is as a display particle dispersion containing display particles and a dispersion medium. Thereby, in the manufacturing method of the display particle which concerns on this embodiment, the particle dispersion liquid for display which used the 1st solvent as the dispersion medium is obtained by passing through the said process, without passing through a washing | cleaning and drying process. Further, the particles may be washed (removal of ionic impurities) or the dispersion medium may be replaced.

  In addition, the manufacturing method of the display particles is not limited to the above-described manufacturing method, and for example, colored particles (display particles) by a known method (pulverization method, coacervation method, dispersion polymerization method, suspension polymerization method, or the like). The method of forming is adopted. In each method, a dispersion medium used for a display medium may be used as a solvent (a solvent finally remaining in the manufacturing method), and the display medium may be used as a display particle dispersion liquid including display particles and a dispersion medium after production. Thereby, in the manufacturing method of the display particle, the display particle dispersion liquid using the solvent to be used as the dispersion medium can be obtained through the manufacturing process without passing through the washing / drying process. Further, the particles may be washed (removal of ionic impurities) or the dispersion medium may be replaced.

Through the above steps, display particles are obtained, and a display particle dispersion containing the display particles is obtained.
Here, the obtained display particle dispersion may be diluted with a dispersion medium (solvent), for example, as necessary. In order to obtain a display particle dispersion containing two or more kinds of display particles, these dispersions may be prepared and then mixed.

  In the display particle dispersion according to the present embodiment, an acid, an alkali, a salt, a dispersant, a dispersion stabilizer, a stabilizer for anti-oxidation or ultraviolet absorption, an antibacterial agent, an antiseptic, and the like, if necessary. May be added. In addition, a charge control agent may be added to the display particle dispersion according to this embodiment.

  The concentration of the display particles in the display particle dispersion according to the present embodiment is variously selected depending on display characteristics, response characteristics, or use thereof, but is selected in a range of 0.1% by mass to 30% by mass. Is desirable. When mixing particles of different colors, it is desirable that the total amount of particles be in this range.

The display particle dispersion according to this embodiment is used for an electrophoretic display medium, an electrophoretic light control medium (light control element), a liquid toner of a liquid developing electrophotographic system, and the like. In addition, as an electrophoretic display medium and an electrophoretic light control medium (light control element), a known method of moving a particle group in a direction opposite to an electrode (substrate) surface, unlike the electrode (substrate), There is a method of moving in a direction along a plane (so-called in-plane type element), or a hybrid element combining these.
In the display particle dispersion according to the present embodiment, color display can be realized by using a mixture of a plurality of types of particles having different colors and charge polarities as display particles.

(Display medium, display device)
Hereinafter, examples of the display medium and the display device according to the embodiment will be described.

  FIG. 1 is a schematic configuration diagram of a display device according to the present embodiment. FIG. 2 is an explanatory diagram schematically illustrating a movement mode of the particle group when a voltage is applied between the substrates of the display medium of the display device according to the present embodiment.

  The display device 10 according to the present embodiment includes the display particle dispersion according to the present embodiment as a particle dispersion including the dispersion medium 50 of the display medium 12, the particle group 34, and a linear polymer (not shown). Is a form to apply. That is, a dispersion medium containing silicone oil is applied as the dispersion medium 50, a group of first display particles is applied as the particle group 34, and silica particles (not shown) are dispersed in the dispersion medium 50. .

  As shown in FIG. 1, the display device 10 according to the present embodiment includes a display medium 12, a voltage application unit 16 that applies a voltage to the display medium 12, and a control unit 18.

  The display medium 12 includes a display substrate 20 that serves as an image display surface, a rear substrate 22 that faces the display substrate 20 with a gap, and holds a space between these substrates at a specific interval, and between the substrates of the display substrate 20 and the rear substrate 22. The gap member 24 is configured to include a reflective particle group 36 having optical reflection characteristics different from that of the particle group 34 enclosed in each cell.

  The cell indicates a region surrounded by the display substrate 20, the back substrate 22, and the gap member 24. A dispersion medium 50 is enclosed in this cell. The particle group 34 is composed of a plurality of particles. The particle group 34 is dispersed in the dispersion medium 50 and reflects between the display substrate 20 and the back substrate 22 according to the electric field strength formed in the cell. Move through the gap.

  In addition, the gap member 24 is provided so as to correspond to each pixel when the image is displayed on the display medium 12, and cells are formed so as to correspond to each pixel, so that the display medium 12 can display each pixel. It may be configured to do.

  Further, in the present embodiment, in order to simplify the description, the present embodiment will be described using a diagram focusing on one cell. Hereinafter, each configuration will be described in detail.

  First, the pair of substrates will be described. The display substrate 20 has a configuration in which a surface electrode 40 and a surface layer 42 are sequentially laminated on a support substrate 38. The back substrate 22 has a configuration in which a back electrode 46 and a surface layer 48 are laminated on a support substrate 44.

  The display substrate 20 or both the display substrate 20 and the back substrate 22 are translucent. Here, the translucency in the present embodiment indicates that the visible light transmittance is 60% or more.

  Examples of the material of the support substrate 38 and the support substrate 44 include glass and plastics such as polyethylene terephthalate resin, polycarbonate resin, acrylic resin, polyimide resin, polyester resin, epoxy resin, and polyethersulfone resin.

  As materials for the front electrode 40 and the back electrode 46, oxides such as indium, tin, cadmium and antimony, composite oxides such as ITO, metals such as gold, silver, copper and nickel, organic materials such as polypyrrole and polythiophene, etc. Is mentioned. The surface electrode 40 and the back electrode 46 may be any of these single-layer films, mixed films, and composite films. The thicknesses of the front electrode 40 and the back electrode 46 are preferably, for example, 100 mm or more and 2000 mm or less. The back electrode 46 and the surface electrode 40 may be formed in a matrix shape or a stripe shape, for example.

  Further, the surface electrode 40 may be embedded in the support substrate 38. Further, the back electrode 46 may be embedded in the support substrate 44. In this case, the materials of the support substrate 38 and the support substrate 44 are selected according to the composition of each particle of the particle group 34 and the like.

  The back electrode 46 and the surface electrode 40 may be separated from the display substrate 20 and the back substrate 22 and disposed outside the display medium 12.

  In the above description, the case where both the display substrate 20 and the back substrate 22 are provided with electrodes (the front electrode 40 and the back electrode 46) has been described. However, only one of them is provided, and active matrix driving is performed. Also good.

  In order to perform active matrix driving, the support substrate 38 and the support substrate 44 may include a TFT (Thin Film Transistor) for each pixel. The TFT is preferably provided on the back substrate 22 instead of the display substrate.

  Next, the surface layer will be described. The surface layer 42 and the surface layer 48 are formed on the surface electrode 40 and the back electrode 46, respectively. Examples of the material constituting the surface layer 42 and the surface layer 48 include polycarbonate, polyester, polystyrene, polyimide, epoxy, polyisocyanate, polyamide, polyvinyl alcohol, polybutadiene, polymethyl methacrylate, copolymerized nylon, ultraviolet curable acrylic resin, fluorine Examples thereof include resins.

  The surface layer 42 and the surface layer 48 may be configured to include the above-described resin and a charge transport material, or may be configured to include a self-supporting resin having a charge transport property.

  Next, the gap member will be described. The gap member 24 for holding a gap between the display substrate 20 and the back substrate 22 is made of, for example, a thermoplastic resin, a thermosetting resin, an electron beam curable resin, a photocurable resin, rubber, metal, or the like. The

The gap member 24 may be integrated with either the display substrate 20 or the back substrate 22. In this case, the support substrate 38 or the support substrate 44 is manufactured by performing etching processing, laser processing processing, press processing processing, printing processing, or the like using a previously manufactured mold.
In this case, the gap member 24 is fabricated on either the display substrate 20 side, the back substrate 22 side, or both.

  The gap member 24 may be colored or colorless, but is preferably colorless and transparent. In that case, the gap member 24 is made of, for example, a transparent resin such as polystyrene, polyester, or acrylic.

The particulate gap member 24 is also preferably transparent, and glass particles are used in addition to transparent resin particles such as polystyrene, polyester, or acrylic.
Note that “transparent” means having a transmittance of 60% or more with respect to visible light.

  Next, the reflective particle group will be described. The reflective particle group 36 is composed of reflective particles having optical reflection characteristics different from that of the particle group 34, and functions as a reflective member that displays a color different from that of the particle group 34. And it also has a function as a gap member to move without hindering movement between the display substrate 20 and the back substrate 22. That is, each particle of the particle group 34 is moved from the back substrate 22 side to the display substrate 20 side or from the display substrate 20 side to the back substrate 22 side through the gap between the reflective particle groups 36. As the color of the reflective particle group 36, for example, white or black is preferably selected so as to be the background color, but other colors may be used. The reflective particle group 36 may be an uncharged particle group (that is, a particle group that does not move in response to an electric field) or a charged particle group (a particle group that moves in response to an electric field). May be. In the present embodiment, the case where the reflective particle group 36 is an uncharged particle group and is white is described, but the present invention is not limited to this.

  The particles of the reflective particle group 36 include, for example, a white pigment (for example, titanium oxide, silicon oxide, zinc oxide), a resin (for example, polystyrene resin, polyethylene resin, polypropylene resin, polycarbonate resin, polymethyl methacrylate resin (PMMA), acrylic resin). Resin, phenol resin, formaldehyde condensate, etc.). Moreover, when applying particles other than white as the particles of the reflective particle group 36, for example, the above-described resin particles containing a pigment or dye of a desired color may be used. If the pigment or dye is, for example, RGB or YMC color, a general pigment or dye used for printing ink or color toner can be used.

  In order to enclose the reflective particle group 36 between the substrates, for example, an inkjet method or the like is performed. Further, when the reflective particle group 36 is fixed, for example, after the reflective particle group 36 is sealed, the particle group surface layer of the reflective particle group 36 is melted by heating (and pressurizing if necessary). It is performed while maintaining the gap.

  The size of the cell in the display medium 12 is closely related to the resolution of the display medium 12, and the smaller the cell, the higher the resolution of the display medium 12 can be produced. The length of the display substrate 20 in the plate surface direction is about 10 μm or more and 1 mm or less.

  In order to fix the display substrate 20 and the back substrate 22 to each other through the gap member 24, fixing means such as a combination of bolts and nuts, a clamp, a clip, and a substrate fixing frame are used. Also, fixing means such as an adhesive, heat melting, and ultrasonic bonding may be used.

  The display medium 12 configured as described above includes, for example, a bulletin board, a circulation version, an electronic blackboard, an advertisement, a signboard, a flashing sign, an electronic paper, an electronic newspaper, an electronic book, and a copier / printer in which images are stored and rewritten. Used for document sheets etc.

  As described above, the display device 10 according to the present embodiment includes the display medium 12, the voltage application unit 16 that applies a voltage to the display medium 12, and the control unit 18 (FIG. 1). reference).

  The voltage application unit 16 is electrically connected to the front electrode 40 and the back electrode 46. In the present embodiment, the case where both the front electrode 40 and the back electrode 46 are electrically connected to the voltage application unit 16 will be described. However, one of the front electrode 40 and the back electrode 46 is grounded. The other may be connected to the voltage application unit 16.

  The voltage application unit 16 is connected to the control unit 18 so as to exchange signals.

  The control unit 18 stores in advance various programs such as a CPU (Central Processing Unit) that controls the operation of the entire apparatus, a RAM (Random Access Memory) that temporarily stores various data, and a control program that controls the entire apparatus. Further, it may be configured as a microcomputer including a ROM (Read Only Memory).

  The voltage application unit 16 is a voltage application device for applying a voltage to the front electrode 40 and the back electrode 46, and applies a voltage according to the control of the control unit 18 between the front electrode 40 and the back electrode 46.

  Next, the operation of the display device 10 will be described. This operation will be described according to the operation of the control unit 18.

Here, a case where the particle group 34 enclosed in the display medium 12 is positively charged will be described. In the following description, it is assumed that the dispersion medium 50 is transparent and the reflective particle group 36 is white. That is, in the present embodiment, a case will be described in which the display medium 12 displays the color exhibited by the movement of the particle group 34 and displays white by the reflective particle group 36 as the background color.
In addition, the following operation | movement demonstrates the operation | movement from the state in which the particle group 34 adhered to the back substrate 22 side on description.

  First, an operation signal indicating that the voltage is applied so that the front electrode 40 becomes a negative electrode and the back electrode 46 becomes a positive electrode for a specific time is output to the voltage application unit 16. When the voltage applied between the electrodes is increased from the state shown in FIG. 2A and a voltage equal to or higher than the threshold voltage at which the surface electrode 40 is a negative electrode and the concentration fluctuation ends is applied, the cohesive force of the particle group 34 is increased. In a reduced state, the particles constituting the particle group 34 charged to the positive electrode move to the display substrate 20 side and reach the display substrate 20 (see FIG. 2B).

  When the application between the electrodes is finished, the particle group 34 is constrained on the surface substrate 20 side, and the color exhibited by the particle group 34 is viewed from the display substrate 20 side with the white color as the color of the reflective particle group 36 being the background color. The color of the display medium 12 is visually recognized.

  Next, an operation signal indicating that a voltage is applied between the surface electrode 40 and the back electrode 46 so that the surface electrode 40 becomes a positive electrode and the back electrode 46 becomes a negative electrode for a specific time is applied to the voltage application unit 16. Output to. When the voltage applied between the electrodes is increased and a voltage equal to or higher than the threshold voltage at which the surface electrode 40 is the positive electrode and the concentration fluctuation ends is applied, the positive electrode is charged in a state where the cohesive force of the particle group 34 is reduced. The particles constituting the particle group 34 move to the back substrate 22 side and reach the back substrate 22 (see FIG. 2A).

  When the application between the electrodes is finished, the particle group 34 is constrained on the back substrate 22 side, while white as the color of the reflective particle group 36 is the color of the display medium 12 visually recognized from the display substrate 20 side. As visible. In addition, the particle group 34 is concealed by the reflective particle group 36 and is difficult to be visually recognized.

  Here, the voltage application time between the electrodes may be stored in advance in a memory such as a ROM (not shown) in the control unit 18 as information indicating the voltage application time in voltage application during operation. Then, information indicating the voltage application time may be read when the process is executed.

  Thus, in the display device 10 according to the present embodiment, the display is performed by the particle group 34 reaching the display substrate 20 or the back substrate 22 and adhering / aggregating.

  In the display medium 12 and the display device 10 according to the present embodiment, the surface electrode 40 is provided on the display substrate 20, the back electrode 46 is provided on the back substrate 22, and a voltage is applied between the electrodes (that is, between the substrates). Although the embodiment has been described in which the particle group 34 is moved between the substrates for display, the present invention is not limited thereto. For example, while the surface electrode 40 is provided on the display substrate 20, the gap member is provided with electrodes, and the voltage between the electrodes is The particle group 34 may be moved and displayed between the display substrate 20 and the gap member.

  Further, in the display medium 12 and the display device 10 according to the above-described embodiment, the mode in which one type (one color) of particle group is applied as the particle group 34 has been described. A form to which the above particle group is applied (specifically, for example, a form in which the group of second display particles in the display dispersion according to the present embodiment is applied) may be used.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example A]
(Example A1)
-Preparation of emulsifier A-
1 g of methacrylic acid, 9 g of FM0711 (manufactured by Chisso: Silaplane) and 0.1 g of a polymerization initiator (azobisdimethylvaleronitrile “V-65”, manufactured by Wako Pure Chemical Industries, Ltd.) are dissolved in 10 g of isopropanol, and nitrogen bubbling is performed. The oxygen was removed by the polymerization and polymerization was carried out at 65 ° C. for 8 hours. After the polymerization, purification treatment and drying were performed to obtain an emulsifier A.

-Production of magenta particles A-
3 g of quinacridone magenta pigment (Ciba) and 7 g of polyacrylic acid (Wako Pure Chemical Industries) were dissolved in 10 ml of water. This was added to a 5% emulsifier A silicone oil solution and emulsified with an ultrasonic emulsifier. The emulsion was depressurized to remove water, and magenta particles A were obtained. Moreover, as a result of measuring the volume average particle diameter of the particles in the dispersion (FPAR-1000: particle diameter analyzer manufactured by Otsuka Electronics Co., Ltd.), it was 600 nm.

-Production of silica particles A-
Silica particles A subjected to alkylation treatment were obtained as follows.
100 g of ethanol, 10 g of water, and 3 g of 30% by mass ammonia water were added and mixed. To this solution, 70 g of tetraethoxysilane, 5 g of polydiorganosiloxane, and 50 g of 1% by mass ammonia water were started and heated to 80 ° C. to obtain a dispersion of spherical polydimethylsiloxane-containing silica particles. To the obtained dispersion, 10 g of hexamethyldisilazane was added at room temperature to trimethylsilylate the silica particles. The dispersion was dried to obtain silica particles A whose surface was alkylated.
The obtained silica particles are obtained by introducing an alkyl group having 1 carbon atom on the surface of monodispersed spherical silica particles having a volume average particle diameter of 100 nm. Further, when the silica particles were examined with a zeta electrometer (Model 502 manufactured by Nippon Luft), they were uncharged particles in the silicone oil.

-Preparation of particle dispersion for display-
0.5 parts by mass of silica particles A per 100 parts by mass of the dispersion medium is added to the obtained magenta particle dispersion containing the magenta particles A (solid content concentration 1.5%), and a display particle dispersion is obtained. Obtained. Table 1 shows the viscosity of the obtained display particle dispersion before and after the addition of silica particles. The viscosity was measured by an automatic micro viscometer (AmVn manufactured by Anton Paar).

(Examples A2 to A9)
A display particle dispersion was obtained in the same manner as in Example A1, except that the concentration of the silica particles A was changed according to Table 1. The viscosity of the obtained display particle dispersion is shown in Table 1.

(Evaluation)
-Production of display media-
A display medium having the same configuration as that of the first embodiment was manufactured as follows (see FIG. 1). An ITO film having a thickness of 50 nm was formed as an electrode on a supporting substrate made of glass having a thickness of 0.7 mm by a sputtering method. After applying a layer to the back substrate composed of this ITO / glass substrate using CYTOP (manufactured by Asahi Glass Co., Ltd., CTL809M), a gap member having a height of 50 μm and a width of 20 μm is obtained by performing exposure and wet etching. Formed.

  After forming a heat-fusible adhesive layer (not shown) on the upper part of the gap member, it was filled with the following white particle group and the obtained display particle dispersion, and ITO / glass produced in the same manner as the back substrate. A display medium having a structure and a treatment layer formed thereon was bonded to the rear substrate so that the surfaces (electrode surfaces) on which the treatment layers were formed opposed to each other, and heated to produce a display medium.

  In this way, a display medium was produced. Using the produced display medium, a voltage of 20 V is applied to both electrodes so that the electrode of the display substrate is positive and the electrode of the rear substrate is negative. By repeating this, particles are moved to the display substrate and the rear substrate, The color of the display particles was displayed.

(Preparation of white particles)
-Preparation of dispersion A-
The following components were mixed, and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion A.
<Composition>
・ Cyclohexyl methacrylate: 53 parts by mass. Titanium oxide 1 (white pigment) (primary particle size 0.3 μm, Type CR63: manufactured by Ishihara Sangyo Co., Ltd.): 45 parts by mass. Cyclohexane: 5 parts by mass.

-Preparation of charcoal dispersion B-
The following components were mixed and finely pulverized with a ball mill in the same manner as described above to prepare a charcoal dispersion B.
<Composition>
-Calcium carbonate: 40 parts by mass-Water: 60 parts by mass

-Preparation of mixture C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution C.
<Composition>
-2% by mass serogen aqueous solution (Daiichi Kogyo Seiyaku): 4.3g
Charcoal cal dispersion B: 8.5g
・ 20% by mass saline solution: 50 g

  35 g of dispersion A, 1 g of divinylbenzene, and polymerization initiator AIBN (azobisisobutyronitrile): 0.35 g were weighed and mixed thoroughly, and deaerated by an ultrasonic machine for 10 minutes. This was added to the mixed solution C and emulsified with an emulsifier. Next, this emulsified liquid was put into a bottle, put into a silicone jar, sufficiently degassed under reduced pressure using an injection needle, and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles. After cooling, cyclohexane was removed from the dispersion with a freeze dryer at −35 ° C. and 0.1 Pa for 2 days. The obtained particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with hydrochloric acid water, and filtered. Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 20 μm and 25 μm to make the particle sizes uniform. This was dried to obtain a white particle group having a volume average particle diameter of 20 μm. This was defined as white particles (reflecting particle group).

-Evaluation-
The display property of the magenta color (memory property) and display characteristics of the obtained display medium were evaluated as follows. The results are shown in Table 1.
When the voltage was applied and the equilibrium state was reached, the color density was measured with X-Rite 530 (X-Rite) (X). After the voltage was released, the color density after 24 hours was measured in the same manner (Y). Y / X was defined as display maintainability. The evaluation criteria are as follows.
◎: 1.5 or more ○: 1.40 or more and less than 1.50 Δ +: 1.30 or more and less than 1.40 Δ −: 1.20 or more and less than 1.30 ×: less than 1.20

When the voltage was applied and the equilibrium state was reached, the color density was measured with X-Rite 530 (X-Rite) to obtain display characteristics. The evaluation criteria are as follows.
A: 98% or more with respect to the initial density B: 90% or more and less than 98% with respect to the initial density Δ +: 85% or more and less than 90% with respect to the initial density Less than x: Less than 75% of the initial concentration

  And the said display maintenance property and evaluation of the display characteristic were each performed in the environment of both normal temperature (25 degreeC) and high temperature (60 degreeC).

[Example B]
(Examples B1 to B9)
Display particle dispersions were obtained and evaluated in the same manner as in Examples A1 to A9 except that a magenta particle dispersion (solid content concentration 1.5%) containing the following magenta particles B was used. The results are shown in Table 1.

-Preparation of emulsifier B-
1 g of 2-acrylamido-2-methylpropanesulfonic acid, 9 g of FM0711 and 0.1 g of a polymerization initiator (V-65) are dissolved in 10 g of isopropanol, oxygen is removed by nitrogen bubbling, and polymerization is performed at 65 ° C. for 8 hours. went. After the polymerization, purification treatment and drying were performed to obtain an emulsifier B.

-Preparation of magenta particles B-
3 g of quinacridone magenta pigment (manufactured by Ciba) and 7 g of dimethylamine / epichlorohydrin polycondensate (manufactured by Yokkaichi Chemical Co., Ltd., Cathiomaster PD-7) were dissolved in 10 ml of water. This was added to a 5% emulsifier A silicone oil solution and emulsified with an ultrasonic emulsifier. The emulsion was depressurized to remove moisture and obtain magenta particles B. Moreover, as a result of measuring the volume average particle diameter of the particles in the dispersion (FPAR-1000: particle diameter analyzer manufactured by Otsuka Electronics Co., Ltd.), it was 500 nm.

[Example C]
(Examples C1 to C9)
Mixing of 50 parts by mass of a cyan particle dispersion (solid content concentration 1.5%) containing the following cyan particles C and 50 parts by mass of a magenta particle dispersion (solid content concentration 1.5%) containing the magenta particles A Display particle dispersions were obtained and evaluated in the same manner as in Examples A1 to A9, except that silica particles A were added to the dispersion. The evaluation was performed for the magenta color of magenta particles and the cyan image retention and display characteristics of cyan particles. The results are shown in Table 2.

-Preparation of emulsifier C-
1 g of phenyl acrylate, 9 g of FM0711, and 0.1 g of a polymerization initiator (V-65) were dissolved in 10 g of isopropanol, oxygen was removed by nitrogen bubbling, and polymerization was performed at 65 ° C. for 8 hours. After the polymerization, purification treatment and drying were performed to obtain an emulsifier C.

-Production of cyan particles C-
3 g of a cyan pigment (manufactured by Ciba) and 7 g of poly (methoxyphenyl acrylate) were dissolved in 10 ml of water. This was added to a 5% emulsifier C silicone oil solution and emulsified by an ultrasonic emulsifier. The emulsion was depressurized to remove moisture and obtain cyan particles C. Further, the volume average particle size of the particles in the dispersion was measured (FPAR-1000: particle size analyzer manufactured by Otsuka Electronics Co., Ltd.), and as a result, it was 700 nm.

[Example D]
(Examples D1 to D3)
Display particle dispersions were obtained and evaluated in the same manner as in Example A2 except that silica particles D1 to D3 were used in accordance with Table 2 instead of silica particles A, respectively. The results are shown in Table 2.

-Production of silica particles D1-
The alkylated silica particles D1 were obtained as follows.
100 g of ethanol, 10 g of water, and 3 g of 30% by mass ammonia water were added and mixed. To this solution, 70 g of tetraethoxysilane, 5 g of polydiorganosiloxane, and 50 g of 2 mass% ammonia water were started, and heated to 80 ° C. to obtain a dispersion of spherical polydimethylsiloxane-containing silica particles. To the obtained dispersion, 10 g of hexamethyldisilazane was added at room temperature to trimethylsilylate the silica particles. The dispersion was dried to obtain silica particles D1 whose surface was alkylated.
The obtained silica particles are obtained by introducing an alkyl group having 1 carbon atom on the surface of monodispersed spherical silica particles having a volume average particle diameter of 50 nm. Further, when the silica particles were examined with a zeta electrometer (Model 502 manufactured by Nippon Luft), they were uncharged particles in the silicone oil.

-Production of silica particles D2-
The alkylated silica particles D2 were obtained as follows.
100 g of ethanol, 10 g of water, and 3 g of 30% by mass ammonia water were added and mixed. To this solution, 70 g of tetraethoxysilane, 5 g of polydiorganosiloxane, and 10 g of 1% by mass ammonia water were started and heated to 80 ° C. to obtain a dispersion of spherical polydimethylsiloxane-containing silica particles. To the obtained dispersion, 10 g of hexamethyldisilazane was added at room temperature to trimethylsilylate the silica particles. The dispersion was dried to obtain silica particles D2 whose surface was alkylated.
The obtained silica particles are obtained by introducing an alkyl group having 1 carbon atom on the surface of monodispersed spherical silica particles having a volume average particle diameter of 300 nm. Further, when the silica particles were examined with a zeta electrometer (Model 502 manufactured by Nippon Luft), they were uncharged particles in the silicone oil.

-Production of silica particles D3-
In the following manner, alkylated silica particles D3 were obtained.
100 g of ethanol, 10 g of water, and 3 g of 30% by mass ammonia water were added and mixed. To this solution, 70 g of tetraethoxysilane, 5 g of polydiorganosiloxane, and 50 g of 1% by mass ammonia water were started, and heated to 80 ° C. to obtain a dispersion of spherical polydimethylsiloxane-containing silica particles. To the obtained dispersion, 10 g of hexaethyldisilazane was added at room temperature to trimethylsilylate the silica particles. The dispersion was dried to obtain silica particles D3 whose surface was alkylated.
The obtained silica particles are obtained by introducing an alkyl group having 2 carbon atoms on the surface of monodispersed spherical silica particles having a volume average particle diameter of 100 nm. Further, when the silica particles were examined with a zeta electrometer (Model 502 manufactured by Nippon Luft), they were uncharged particles in the silicone oil.

[Comparative example]
(Comparative Example 1)
A display particle dispersion was obtained and evaluated in the same manner as in Example A3 except that the silica particles A were not added. The results are shown in Table 2.

(Comparative Examples 2-3)
Display particle dispersions were obtained and evaluated in the same manner as in Example A3 except that the following particles E1 to E2 were used instead of silica particles A, respectively. The results are shown in Table 2.

-Particle E1 (not subjected to alkylation treatment)
In the following manner, comparative silica particles E1 not subjected to alkylation treatment were obtained.
100 g of ethanol, 10 g of water, and 3 g of 30% by mass ammonia water were added and mixed. To this solution, 70 g of tetraethoxysilane, 5 g of polydiorganosiloxane, and 50 g of 1% by mass ammonia water were started, and heated to 80 ° C. to obtain a dispersion of spherical polydimethylsiloxane-containing silica particles E1.
The obtained silica particles are monodispersed spherical silica particles having a volume average particle diameter of 100 nm. Further, when the silica particles were examined with a zeta electrometer (Model 502 manufactured by Nippon Luft), they were negative electric particles in the silicone oil.

-Particle E2-
As particles E2, particles of melamine / formaldehyde condensate (Eposter S, manufactured by Nippon Shokubai Co., Ltd.) were prepared.
The particles E2 are organic particles having a volume average particle diameter of 200 nm. Further, when the particle E2 was examined with a zeta electrometer (Model 502 manufactured by Nippon Luft), it was an electroless particle in the silicone oil.

(Comparative Example 4)
A display particle dispersion was obtained and evaluated in the same manner as in Example A3 except that 1 part by mass of the following polymer was used in place of silica particle A. The results are shown in Table 2.

-Production of polymer 1-
A polymer was obtained as follows.
10 g of FM0711, 0.03 g of the polymerization initiator (V-65) and 2 g of isopropanol were mixed, degassed by bubbling with nitrogen gas, and then subjected to a polymerization reaction at 65 ° C. for 6 hours. After the polymerization, the solvent was removed under reduced pressure to obtain a polymer.

From the obtained results, it can be seen that in this example, superior results were obtained in both display sustainability and display characteristics as compared with the comparative example.
In this example, it is considered that bridging aggregation occurs on the low concentration side of the silica particles and depletion aggregation occurs on the high concentration side of the silica particles.

[Example E]
(Preparation of emulsifier)
-Production of emulsifier E1-
1 g of methacrylic acid, 9 g of FM0711 (manufactured by Chisso: Silaplane) and 0.1 g of a polymerization initiator (azobisdimethylvaleronitrile “V-65”, manufactured by Wako Pure Chemical Industries, Ltd.) are dissolved in 10 g of isopropanol, and nitrogen bubbling is performed. The oxygen was removed by the polymerization and polymerization was carried out at 65 ° C. for 8 hours. After the polymerization, purification treatment and drying were performed to obtain an emulsifier E1.

-Production of emulsifier E2-
1 g of dimethylaminopropylacrylamide, 9 g of FM0711 (manufactured by Chisso: Silaplane), and 0.1 g of a polymerization initiator (azobisdimethylvaleronitrile “V-65”, manufactured by Wako Pure Chemical Industries, Ltd.) are dissolved in 10 g of isopropanol. Then, oxygen was removed by nitrogen bubbling, and polymerization was carried out at 65 ° C. for 8 hours. After the polymerization, purification treatment and drying were performed to obtain an emulsifier E2.

(Production of magenta particles)
-Production of magenta particles E1-
3 g of quinacridone-based magenta pigment (CibD) and 7 g of polyacrylic acid (Wako Pure Chemical Industries) were dissolved in 10 ml of water. This was added to a silicone oil solution of 5% emulsifier E1 and emulsified with an ultrasonic emulsifier. The emulsion was depressurized to remove water and obtain magenta particles E1. Moreover, as a result of measuring the volume average particle diameter of the particles in the dispersion (FPDR-1000: particle diameter analyzer manufactured by Otsuka Electronics Co., Ltd.), it was 600 nm.

-Production of magenta particles E2-
Magenta particles E2 were obtained in the same manner as the magenta particles E1, except that a silicone oil solution of 5% emulsifier E2 was used instead of the silicone oil solution of 5% emulsifier E1. Moreover, as a result of measuring the volume average particle diameter of the particles in the dispersion (FPDR-1000: particle diameter analyzer manufactured by Otsuka Electronics Co., Ltd.), it was 600 nm.

(Preparation of silica particles)
-Production of silica particles E1-
The alkylated silica particles E1 were obtained as follows.
100 g of ethanol, 10 g of water, and 3 g of 30% by mass ammonia water were added and mixed. To this solution, 70 g of tetraethoxysilane, 5 g of polydiorganosiloxane, and 50 g of 1% by mass ammonia water were started and heated to 80 ° C. to obtain a dispersion of spherical polydimethylsiloxane-containing silica particles. To the obtained dispersion, 10 g of hexamethyldisilazane was added at room temperature to trimethylsilylate the silica particles. The dispersion was dried to obtain silica particles E1 whose surface was alkylated.
The obtained silica particles are obtained by introducing an alkyl group having 1 carbon atom on the surface of monodispersed spherical silica particles having a volume average particle diameter of 100 nm. Further, when the silica particles were examined with a zeta electrometer (Model 502 manufactured by Nippon Luft), they were uncharged particles in the silicone oil.

(Production of mediator polymer)
-Production of mediator polymer E1-
10 g of isopropanol, 2.5 g of dimethylaminoethyl methacrylate (DMAEMA), 7.5 g of FM0711 (manufactured by Chisso: Silaplane), polymerization initiator (azobisdimethylvaleronitrile “V-65”, manufactured by Wako Pure Chemical Industries, Ltd.) 0.1 g was dissolved, oxygen was removed by nitrogen bubbling, and polymerization was carried out at 65 ° C. for 8 hours. After the polymerization, purification treatment and drying were performed to obtain a mediator polymer E1.

-Preparation of mediator polymer E2-
2.5 g of 2-hydroxyethyl methacrylate (HEMA), 7.5 g of FM0711 (manufactured by Chisso: Silaplane), 10 g of isopropanol, polymerization initiator (azobisdimethylvaleronitrile “V-65”, manufactured by Wako Pure Chemical Industries, Ltd.) ) 0.1 g was dissolved, oxygen was removed by nitrogen bubbling, and polymerization was carried out at 65 ° C. for 8 hours. After the polymerization, purification treatment and drying were performed to obtain a mediator polymer E2.

-Production of mediator polymer E3-
10 g of isopropanol, 1 g of dimethylaminoethyl methacrylate (DMAEMA), 1 g of 2-hydroxyethyl methacrylate (HEMA), 8 g of FM0711 (manufactured by Chisso Corporation: Silaplane), a polymerization initiator (azobisdimethylvaleronitrile “V-65”, 0.1 g) (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved, oxygen was removed by nitrogen bubbling, and polymerization was performed at 65 ° C. for 8 hours. After the polymerization, purification treatment and drying were performed to obtain a mediator polymer E3.

  Mediating polymers E4 to E7 were obtained in the same manner as the mediating polymer E3, except that the blending ratio (mass ratio) of FM0711, DMAEMA, and HEMA was changed according to Table 3.

(Examples E1-1 to E1-8)
-Preparation of particle dispersion for display-
In addition to adding 1 part by mass of silica particles E1 per 100 parts by mass of the dispersion medium to the magenta particle dispersion (solid content concentration 1.0%) containing the obtained magenta particles E1, the types according to Table 4 The intermediate polymer was added at an addition concentration (mass% with respect to the dispersion medium) to obtain display particle dispersions E1-1 to E1-8.

(Examples E2-1 to E2-8)
-Preparation of particle dispersion for display-
In addition to adding 1 part by mass of silica particles E1 per 100 parts by mass of the dispersion medium to the magenta particle dispersion (solid content concentration 1.0%) containing the obtained magenta particles E2, the type according to Table 5 The intermediate polymer was added at an addition concentration (mass% with respect to the dispersion medium) to obtain display particle dispersions E2-1 to E2-8.

(Evaluation)
-Production of display media-
An ITO film having a thickness of 50 nm was formed as an electrode on a supporting substrate made of glass having a thickness of 0.7 mm by a sputtering method. After applying Cytop (CTL809M, manufactured by Asahi Glass Co., Ltd.) by spin coating on the back substrate composed of this ITO / glass substrate, a gap member having a height of 50 μm and a width of 20 μm is obtained by performing exposure and wet etching. Formed.
A heat-bondable adhesive layer is formed on the upper part of the gap member, and then the display substrate is filled with display particle dispersion and made of ITO / glass prepared in the same manner as the back substrate, and the treatment layer is formed. The display medium was manufactured by applying heat to the back substrate so that the surfaces (electrode surfaces) on which the treatment layers were formed face each other.

-Evaluation-
A display medium was connected to the function generator, and a voltage of ± 30 V was applied as a triangular wave with a period of 0.5 Hz. The display color change accompanying the particle movement at that time was detected by a reflected light measuring device (Ocean Optics, spectroscope: USB400, light source: LS1). The differential of the voltage-reflectance profile at that time was calculated, and the peak of the voltage-differential profile was defined as the threshold value.
The obtained threshold values are shown in Tables 4 and 5.

From the above results, it can be seen that the example using the intermediary polymer has an increased threshold value and improved image maintainability compared to Examples E1-1 and E2-2 that do not use the intermediary polymer.

DESCRIPTION OF SYMBOLS 10 Display apparatus 12 Display medium 16 Voltage application part 18 Control part 20 Display substrate 22 Back substrate 24 Gap member 34 Particle group 36 Reflective particle group 38 Support substrate 40 Surface electrode 42 Surface layer 44 Support substrate 46 Back electrode 48 Surface layer 50 Dispersion medium

Claims (6)

A dispersion medium containing silicone oil;
First display particles that are dispersed in the dispersion medium and move according to an electric field, the first display particles having a polar group on the surface,
Dispersed in the dispersion medium, having an alkyl group on the surface, and uncharged silica particles;
A particle dispersion for display comprising:   2. The display particle dispersion according to claim 1, comprising second display particles that are dispersed in the dispersion medium and move according to an electric field, and that have second display particles having a nonpolar group on the surface.   3. The display particle dispersion according to claim 1, wherein a polymer composed of a copolymer of a monomer having a polar group and a monomer having a silicone chain is dissolved in the dispersion medium. A pair of substrates, at least one of which is translucent,
The display particle dispersion liquid according to any one of claims 1 to 3, encapsulated between the pair of substrates,
A display medium comprising: A pair of electrodes, at least one of which is translucent,
The area | region which has the particle dispersion liquid for display of any one of Claims 1-3 provided between the said pair of electrodes,
A display medium comprising: A display medium according to claim 4 or 5, and
Voltage application means for applying a voltage between the pair of substrates or the pair of electrodes of the display medium;
A display device comprising: